The insights derived from neuroscience studies of cortical plasticity have been indispensable in the development of treatment strategies for a number of neurological disorders, including dyslexia, tinnitus, and stroke. However, because most of these studies were focused on relatively simple sensory stimuli, our understanding of the plasticity principles that shape the cortical representation of more complex stimuli, such as speech, remains rudimentary. The proposed experiments document how experience-dependent plasticity improves the auditory cortex representation of spectro temporally complex stimuli and, by advancing our understanding of brain mechanisms involved in the learning of language, will aid in the treatment of communicative disorders. Using simple stimuli, we have demonstrated that electrical stimulation of the cholinergic nucleus basalis (NB) generates robust cortical plasticity that parallels natural learning. The proposed experiments will extend this series by pairing NB stimulation with complex spectrotemporal stimuli. Two different coding strategies, which have demonstrated stimulation of the cholinergic nucleus basis (NB) generates robust cortical plasticity that parallels natural learning. The proposed experiments will extend this series by pairing NB stimulation with complex spectrotemporal stimuli. Two different strategies, which have been proposed to represent the neural basis of memory, emerge with natural learning of behaviorally important complexes stimuli. In the first, complex features are represented by the distributed activity of neurons (coarse coding); while in the second, complex stimuli are represented with specialized filters tuned to specific spectrotemporal transitions (sparse coding). Our preliminary evidences indicates that NB-stimulation leads to representational plasticity that combines both coding strategies. In addition to sharpening spectral and temporal responses generally, NB activation paired with a spectrotemporal sequence created combination selective neural responses that do not exist in naive cortex. These results demonstrate that combination selectivity is not limited to species/specific vocalizations, and representations of the acoustic environment. Our continuing studies will examine several other acoustic stimuli to determine precisely what stimulus features are required to generate each element of representational plasticity observed in our preliminary results.